A variety of technologies are used for semiconductor device identification, recognition, authentication, verification, security, and the like; for simplicity of explanation of the present invention, such issues and processes and mechanisms associated with such issues are generically referred to generically as “coding.” For example, to resolve such issues in semiconductor devices—e.g., integrated circuits (ICs), ink-jet printheads, nanomachines, and the like—they are often coded using mechanisms such as bar codes, distinct pattern lithographic features, encryption circuitry, tamper detection circuitry, or activation firmware programming, and the like.
Quantum dots are semiconductor crystals having a size on the order of just a few nanometers. Known manner fabrication of quantum dot constructs is described in the textbook titled “Quantum Dot Heterostructures,” by D. Bimberg, M. Grundmann, and N. N. Ledentsov, copyright, John Wiley & Sons, U.K. publishers, 1998, and in U.S. Pat. No. 6,942,731 by Sellin et al. (including Bimberg, D.), titled “Method For Improving The Efficiency Of Epitaxially Produced Quantum Dot Semiconductor Components,” each incorporated herein by reference.
Quantum dots structures, as in the case of the present invention, may be self-assembling, self-organized constructs that are characterized by electron, hole, or electron-hole pair confinement which results in discrete quantized energy levels and distinct spectral photoluminescence. The larger a quantum dot, the more towards the red end of the spectrum the fluorescence; the smaller the dot, the more towards the blue end. In other words, a quantum dot construct comprising many nanocrystals will exhibit a distinct luminescence spectral emission when reflected light is analyzed by known manner spectroscopy techniques. Because of the heterogenous nature of each quantum dot structure, each will have a unique spectral pattern, analogous to a “signature” or “fingerprint.” See e.g., “Near-Field Spectroscopy of the Quantum Constituents of a Luminescent System,” H.F. Hess et al., Science, vol. 264, 1994, pp. 1740.
In U.S. Pat. No. 6,633,370, for “Quantum Dots, Semiconductor Nanocrystals and Semiconductor Particles Used As Fluorescent Coding Elements,” N.M. Lawandy discusses impediments to using quantum dots for coding, labeling and authentication applications for integrated circuits. Lawandy instead proposes using “semiconductor particles having a radius larger than a quantum dot radius for a corresponding material.”
With semiconductor devices having an ever increasing complexity, continual miniaturization of the discrete components therein, and issues regarding counterfeit products, there is a need for improved semiconductor device coding technologies.